In United States, a tube for connecting nerve tissues by using collagen is already commercially available as NeuraGen nerve guide (trade name) from Integra NeuroCare LLC, USA, and a tube for connecting nerve tissues by using polyglycolic acid (PGA) is commercially available as GEM Neurotube (trade name) from Synovis Micro companies Alliance, USA. These neuron connection tubes are hollow tubes inside which nothing is filled, and can be used for regenerating a peripheral sensory nerve in which a length of a defective part of the nerve is up to 2 cm. When the hollow tubes are implanted in the defective parts of the nerves, nerve fibers are regenerated in the defective parts.
However, when the defective part is longer than 2 cm, the use of the nerve connection tube is limited. This is because in the hollow tube, the potential for promoting the regeneration of nerve is poor and the decomposition thereof is rapid and therefore there are such problems as the hollow tube cannot be used for longer defective parts. Furthermore, in the hollow tubes that are commercially available in United States, there is a problem that if there is an aperture difference between the aperture of the end of the hollow tube and the aperture of the end of the neuron, a gap is generated between both the apertures and therefore surrounding tissue inhibiting the progress of the nerve tissue invades the gap and inhibits the progress of nerve generation. Moreover, there is a problem that when the defective part of the peripheral nerve branches, one hollow tube cannot be used and the implanting operation is troublesome. There is a further problem that the sustainability of the lumen of the hollow tube is insufficient. Therefore a long defective part cannot be repaired, the nerve cannot extend and regeneration stops. Moreover, there is a problem depending on the region used, both ends cannot be inserted in the nerve tube.
Recently, an artificial nerve tube containing sponge-like or gel-like collagen in a tube has been made of a biodegradable absorbable material (such as polylactic acid and polyglycolic acid). For example, Patent Document 1 (WO 98/22155) discloses an artificial nerve tube containing a gel consisting of collagen and laminin in a tube made of a biodegradable absorbable material (such as polylactic acid and polyglycolic acid).
Patent Document 2 (Japanese Unexamined Patent Publication (Kokai) No. 2003-019196) discloses a tube for regenerating nerve which is made of an outer layer of a bioabsorbable material (such as polylactic acid) and an inner layer made of a sponge-like substance of collagen and a lactic acid/ε-caprolacton copolymer.
Patent Document 3 (Japanese Unexamined Patent Publication (Kokai) No. 2004-208808) discloses an inductive tube for nerve regeneration containing a sponge-like collagen inside a tubular body made of a biodegradable material or bioabsorbable material (such as protein, polysaccharide, polylactic acid, and polyglycolic acid).
Patent Document 4 (Japanese Unexamined Patent Publication (Kokai) No. 2005-143979) discloses a nerve-regenerating tube in which fiber-like synthetic bioabsorbable polymer (such as polylactic acid and polyglycolic acid) coated with collagen is filled inside a tubular body made of bioabsorbable material polymer (such as polylactic acid and polyglycolic acid).
Non-Patent Document 1 (Lee D Y et al, Journal of Cranio-Maxillofacial Surgery (2006) 34, 50-56, “Nerve regeneration with the use of a poly-L-lactide-co-glycolic acid-coated collagen tube filled with collagen gel”) discloses an artificial nerve tube containing a gel-like collagen in a tubular body made of polylactic acid and polyglycolic acid.
In Patent Documents 1 to 4 and Non-Patent Document 1, collagen having a sponge-like, gel-like, or fiber-like structure is included inside a biodegradable material of a tubular body, and therefore, compared to a hollowing body containing no collagen, the collagen serves as a so-called scaffold for nerve regeneration, and thereby, there is an advantage that the nerve regeneration is more promoted.
However, additional there is an increasing need for not only for promotion of nerve tissue regeneration and assisting tissue restoration, but also for improvement of clinical performance by accelerating recovery of physiological functions of nerve tissue. Moreover, there are such problems that clinical application is not possible because laminin which is a physiologically active substance the security of which is yet to be established is used, that the tubes cannot be used for longer defective parts because the decomposition thereof is rapid, that a gap is generated if there is an aperture difference between the artificial nerve and cut end of the nerve, that the tubes cannot be used if a branch exists, that the sustainability of the lumen is also insufficient and that occasionally both ends cannot be inserted into the neural tube.